It is kind of hilarious to argue about the skin color of people millennia from now as if they would be static. Considering the amount of globalization, I would expect humanity to look quite different in a couple of hundred years already. If there are major visible differences between people 10k years in the future, they probably are along planet boundaries, and in which way they express is difficult to estimate. UV radiation might still play a huge role in skin coloring, but there could be many other differentiators being common.